1. Field of the Invention
The invention relates to a colored photosensitive curing composition that are used favorably in production of a color filter for use in liquid crystal display elements and solid-state image sensing devices, a color filter, and a method for producing the same.
2. Description of the related Art
A pigment dispersion method has been used as one of the methods for producing color filters for use in liquid crystal display elements and solid-state image sensing devices. The pigment dispersion method is a method of producing a color filter by photolithography, by using a colored radiation-sensitive composition containing a pigment dispersed in various kinds of photosensitive compositions. The method, which uses a pigment and provides a color filter resistant to light and heat and favorable in positioning accuracy because of patterning by photolithography, has been used widely as a favorable method in producing color filters for large-screen, high-resolution color displays.
In preparing a color filter by the pigment dispersion process, the radiation-sensitive composition is first coated on a substrate with a spin coater or roll coater and dried to form a coating film. Then, colored pixels are obtained by patterned-exposure and development of the coating film. The color filter can be prepared by repeating this operation a number of times corresponding to the number of hues.
Recently, in the color filter for solid state image sensing devices, even higher resolution has become desirable, but the conventional pigment dispersions have difficulties in further improving the resolution. Because of problems such as the generation of color irregularities due to coarse particles of the pigment, it is not suitable for uses which require fine patterns such as solid state image sensing devices.
Use of a dye as the colorant has been conventionally studied from the viewpoint of improvement in the resolution above (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 6-75,375). However, such dye-containing curing compositions have the following additional problems:
(1) Dyes are generally lower in light stability and heat resistance than pigments.
(2) It is difficult to obtain a liquid curing composition having a desired spectrum with a common colorant, because such a colorant is less soluble in aqueous alkaline solution or organic solvent (hereinafter, suitably referred to as solvent).
(3) It is difficult to control the solubility (printing efficiency) of the cured area and the uncured area, because the dye used often interacts with other components in the curing composition.
(4) When the molar absorption coefficient (8) of the dye used is low, the dye needs to be added in a larger amount and thus, the amounts of the other components in the curing composition such as polymerizable compound (monomer), binder, and photopolymerization initiator must be reduced, which leads to deterioration in the curing efficiency of the composition, the heat resistance after curing, and the developing efficiency of the (non) cured area.
Due to these problems, it has been difficult to form colored patterns that are detailed and have a thin film in high-resolution color filters. Unlike those used in the production of semiconductors, it is necessary to use a thin film of 1 μm or less in thickness for the production of color filters for solid-state image sensing devices. It is thus necessary to add a colorant to the curing composition in a larger amount for obtaining a desired absorption, leading to the problems described above.
Hereinafter, conventional technology concerning high-fastness dye will be described. Generally, all colorants used in various applications preferably have the following properties: light absorption properties favorable for color reproduction, favorable levels of stability, such as good heat resistance, light stability, and moisture resistance, under the environment in which it is used, a molar absorption coefficient large enough to allow reduction in film thickness, and others.
For example, dipyrromethene-based metal complexes are known to be used as a functional compound in various applications and also as a sensitizer for the radical polymerization initiator in visible light-sensitive photopolymerization compositions (see, e.g., Japanese Patent Nos. 3,279,035 and 3,324,279, and JP-A Nos. 11-352,685, 11-352,686, 2000-19,729, 2000-19,738 and JP-A No. 2002-236,360). They are also known to be used, not as a colorant for red, green, or blue pixels in liquid crystal displays and electronic displays, but as a colorant for filters, for eliminating undesired emissions from, for example, plasma emission devices and liquid crystal displays (see, e.g., JP-A Nos. 2003-57,436, 2005-77,953, 2006-651,121, 2006-79,011 and 2006-79,012).